PROTEASE STABILIZATION BY HIGHLY CONCENTRATED ANIONIC SURFACTANT MIXTURES

We have found that anionic surfactants such as linear alkylbenzene sul fonate (LAS) can solubilize proteases in a substantially nonaqueous en vironment without loss of proteolytic activity. Moreover, in mixtures of anionic and nonionic surfactants with a moderate amount of water (w ater less than 30 wt%), controlled levels of LAS and water solubilize pro teases; yet, in these concentrated surfactant mixtures, enzymes ma intain their activity for extended periods. Experimental design techni ques have been used to delineate the relationship between protease sta bility and the water, pH and anionic surfactant levels in these surfac tant concentrates. As the sum of water and LAS levels is increased, ma ximum enzyme stability is observed, after which stability falls off. A t low water and LAS levels (sum of both <20%), protease solubility is low, while at high levels of water and LAS (sum of LAS and water >45%) , denaturation predominates. Additionally, we have developed a new and simple method to predict protease stability by which a synthetic pept ide is used to measure protease activity directly in the surfactant co ncentrate. From the application or this new technique to our system an d to commercial liquid detergent formulations, it is apparent that wat er facilitates the loss of activity of proteases in surfactant concent rates by increasing the rate of autolysis.